The present invention relates to an improved device for shutting off the air intake passage of engines. The present invention more particularly relates to an improved apparatus which can safety and efficiently close the air intake passages of diesel engines in emergency situations such as for example when the presence of airborne hydrocarbons threatens controlled engine operation. Even more particularly, the present invention relates to an air intake shutoff apparatus which may be installed over an engine air intake passage such as for example between the engine blower and the engine air filter. The apparatus generally consists of an air passage shutoff assembly, an actuator assembly which can be powered for example pneumatically or hydraulically, and a control assembly which can be activated either automatically or remote-manually. The air passage shutoff assembly has an airtight frame which can be fitted over the air intake passages of an engine, such as may be found on an engine blower. The frame has an air intake passage which has substantially the same size and shape as the air intake passage of the engine. A baffle plate whose movement is guided by rotatable, retractable baffle arms which slide across the air intake passage to close the air passage once a power source such as a pneumatic actuator assembly is activated by a control system which may be either automatic or remote-manual.
Federal regulations now require engine air intake shutoff devices to be installed on all engines where there is a potential for hydrocarbons to be in the atmosphere in which the engine is operating. These regulations will be applicable to mobile offshore drilling units on May 31, 1989.
Some prior art air intake shutoff devices including control systems currently available are priced in excess of $10,000.00 per device, exclusive of installation costs. Mobile offshore drilling units typically have four to ten engines. Some smaller engines may have one blower typically requiring one air intake shutoff device, while larger engines may have two air intake shutoff devices. Thus operators of mobile offshore drilling units are required to make a substantial capital outlay in order to comply with the regulations.
Some prior art air intake shutoff devices such as flapper valves and guillotine type devices are large and have dimensions that exceed the space limitations existing in the hulls of mobile offshore drilling units or vessels.
Some prior art air intake shutoff devices are activated by a gas that will not support combustion, such as for example carbon dioxide. The gas is contained in cylinders until the devices are activated. Once the devices are activated, the gas is injected into the engine intake air stream, displacing the intake air with the inert gas. When engine shutdown is completed, excess gas may escape the engine causing a threat to personnel in the area. In addition, after the gas has been disbursed from the cylinders, the cylinders must be returned to an onshore site to be refilled before the engine can again be operated in compliance with the federal regulations.
Some prior art air intake shutoff devices are not synchronized to allow the engine fuel system to begin shutdown prior to or simultaneously with the activation of the engine air intake shutoff device. When there has been a shutdown of the engine air intake device without coordination with the engine's fuel system shutdown, several problems have arisen. First, the engine air boxes or intake air chambers surrounding the engine's cylinder liners are subject to excessive pressure and possible damage. Second, the air box or hand hole covers on the cylinders have been known to have been blown away from their seats and cause the threat of injury to personnel working in the area.
Some prior art air intake shutoff devices, such as for example, guillotine type or flapper valves which close instantly or almost instantly do not have means for providing a controlled rate of closure of the engine's air intake passage. With instantaneous closure, pneumatic shock occurs to the engine's air intake system resulting in rapid vacuum and air pressure changes. The pneumatic shock may cause the engine's blowers or superchargers and the engine itself to be damaged.
Various prior art devices for shutting down an engine by preventing air from flowing through an engine air intake passage, as well as the apparatus and method of this construction, in general, are known, and found to be exemplary in an undated letter from the Minerals Management Service, United States Department of the Interior to the International Association of Drilling Contractors. The letter notes that there are three types of devices for shutting down a diesel engine. First, there are positive shutoff valves in the engine air intake. Second, there are devices which combine positive shutoff valves in the air intake with either decompression of the engine, or shutting off the fuel supply or modifying the engine to alter its crankcase ventilation air flow. Third, there are devices which will inject a gas that will not support combustion into the engine air intake. Representative companies that have developed these types of devices include the following:
1. Hunt Engine Company of Harvey, La. has a shutoff valve for use on V-8 Electro-Motive Diesel (EMD) engines, known as the "Motokill" system. The system uses a flapper valve to shut off the air flow through the engine air intake passage.
2. Gulf Coast Manufacturing of Houma, La. has a spring-loaded check valve to shut down Deutz diesel engines.
3. Delhomme Industries of New Iberia, La. has a combination air intake shutoff valve and decompression activation kit that can be used on Lister diesel engines. Delhomme also has an air intake shutoff valve that can be used on Onan diesel engines.
4. Amot Controls Corporation has a shutoff valve which uses a rotating butterfly disc valve to close the engine air intake passage.
5. Barber Industries, a division of Bralorne Resources Limited offers a device known as a "Rig Saver Valve" which uses a swing gate to close the engine air intake passage.
6. The Farr Company offers a guillotine valve, known as the "Slammer" which is designed to shut down the engine of diesel-electric locomotives.